1. Field of the Invention
The present invention relates to a radiation cassette provided with a lid which is installed to a part of a casing for accommodating a radiation image record carrier so that the lid is openable and closable.
2. Description of the Related Art
For example, a system is known, in which an accumulative fluorescent material (stimulus fluorescent material) is utilized to once record radiation image information of an object such as a human body so that the radiation image information is reproduced, for example, on a photographic photosensitive material such as a photographic film, or the information is outputted as a visible image to CRT or the like.
The accumulative fluorescent material is a fluorescent material which accumulates a part of energy of a radioactive ray in accordance with radiation of the radioactive ray (for example, X-rays, xcex1-rays, xcex3-rays, electron beams, ultraviolet radiation) and which exhibits stimulus light emission corresponding to the accumulated energy by being irradiated with an excitation light beam such as visible light thereafter. Usually, the accumulative fluorescent material is constructed to have a sheet-shaped configuration, and it is used as an accumulative fluorescent material sheet.
On the other hand, an operation is performed, in which a radioactive ray such as X-rays is radiated onto a object such as a human body so that radiation image information of the object is directly recorded on a photographic film. A visible image is obtained by applying a development treatment to the photographic film, and the visible image is used to perform, for example, the medical diagnosis.
Usually, the radiation image record carrier such as the accumulative fluorescent material sheet and the photographic film as described above is charged to a photographing apparatus in a state in which the radiation image record carrier is accommodated one by one in a cassette. The radiation image record carrier is irradiated with the X-rays through the cassette.
Those known as such a cassette include, for example, a cassette disclosed in Japanese Patent Publication No. 6-90424 or Japanese Laid-Open Patent Publication No. 7-36131. As shown in FIG. 17, the cassette described above comprises a casing 2 which accommodates a radiation image record carrier 1, a lid 3 which is installed to a part of the casing 2 to be openable and closable, and a shield plate 4 which is arranged for a residual portion of the casing 2 and which holds the radiation image record carrier 1 in a light-shielding manner together with the lid 3.
If any dust or the like exists at the inside of the cassette, the dust or the like may adhere to the radiation image record carrier 1. It is feared that a defective image is recorded on the radiation image record carrier 1 by being irradiated with the radioactive ray. For this reason, when a high quality image is required especially in the case of the use of a mammocassette, it is necessary to frequently clean the interior of the cassette.
However, in the case of the cassette described above, the shield plate 4 is usually fixed to the casing 2 by the aid of a plurality of screws. It is considerably complicated to perform the operation for detaching the shield plate 4. Therefore, a problem is pointed out such that it takes a considerable period of time to perform the operation for cleaning the interior of the cassette.
Usually, it is necessary to provide a lead sheet in the cassette corresponding to a back surface side (side of the surface opposite to the surface irradiated with the radioactive ray) of the radiation image record carrier 1. As shown in FIG. 18, lead sheets 5a, 5b are also arranged for the cassette described above. That is, the lid 3 is constructed to be openable and closable with a hinge section 6. In order to avoid the occurrence of any damage caused by bending or folding of the lead sheet, the arrangement is made in a divided manner with the lead sheet 5a which is secured to the back surface of the shield plate 4 to extend in the casing 2 and the lead sheet 5b which is secured to the back surface of the lid 3.
However, in the case of the cassette described above, a wrap section 7, at which the lead sheets 5a, 5b are overlapped with each other, exists in the cassette, because the divided lead sheets 5a, 5b are used. Therefore, the thickness of lead differs between the wrap section 7 and the other sections. A problem is pointed out such that any nonuniformity of an image due to scattered rays is generated on a radiation image recorded on the radiation image record carrier 1.
A general object of the present invention is to provide a radiation cassette which makes it possible to efficiently clean the interior of the radiation cassette having a lid which is installed to a part of a casing to be openable and closable, by means of simple operation.
A principal object of the present invention is to provide a radiation cassette which makes it possible to reliably avoid, with a simple arrangement, the occurrence of nonuniformity of an image on a radiation image record carrier in the cassette.
The above and other objects, features, and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which a preferred embodiment of the present invention is shown by way of illustrative example.